Power loom with a device for cutting off a woof thread

ABSTRACT

A weaving machine, in particular an airjet loom, which is fitted with a system ( 16 ) for cutting a filling thread ( 12 ′), which is being held ready for filling insertion, from a filling ( 12 ) already beaten into a fabric ( 10 ), wherein the system ( 16 ) includes a laser.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/069,121 filed on Mar. 1, 2002 now U.S. Pat. No. 6,763,854.

BACKGROUND

A. Field

The invention relates to a weaving machine with a system for cutting afilling thread that is held ready for filling insertion from a fillingthread already beaten into a woven fabric.

B. Related Art

When weaving, a filling thread inserted into a shed is beaten by a reedagainst the fabric edge, the so-called fell line. Before the fillingthread is inserted into the next shed, it is cut off on the insertionside of the shed. The filling thread awaiting insertion should be cut ata precisely defined time in order to control the length of the nextinserted filling and/or the thread tension and to satisfy otherconditions.

In a known weaving machine of the above described kind (European patentdocument 0 284 766 A1), the filling thread is cut by a mechanical cutterwhich contains a drive that is separate from the main machine drive andthat in turn is controlled by a programmable control system.

SUMMARY OF THE INVENTION

The objective of the invention is to design the system of the above kindso that even more precise timing of the cutting can be achieved.

This problem is solved by using a laser as the cutting device.

The invention offers the advantage that such a laser can be actuatedvery rapidly and that as a result the cutting of the filling can becarried out in a fraction of a second. Moreover such a laser operateswithout mechanical components that are subject to wear, and consequentlya predetermined precise cutting time can be maintained without effect ofany wear. The design of the invention provides the further followingadvantage when the filling is made of a synthetic material, for instancea filament thread or one containing synthetic components. Such syntheticmaterial will be slightly fused when cut so that the fibers of thefilament threads of the cut ends are bonded to one another. This featureis especial advantageous in airjet looms. In airjet looms there is adanger that the filling that is kept ready in a main blowing nozzle mayfray in the vicinity of its end or may unravel. If this occurs, problemswill arise during the subsequent filling insertion because of theincreased danger of catching of the fibers on the teeth of the reed.Also, the appearance of fabric edge opposite the insertion side wouldthen be degraded. Therefore the invention provides an advantage withrespect to airjet looms. As regards other machinery, for instancegripper looms, the invention also offers substantial advantages, inparticular with regard to the accurate determination of the time ofcutting.

Cutting systems in the form of lasers are basically known in the textileindustry, for instance from the Italian patent 1,140,124, the Dutchpatent 175,326 and the Japanese patent document 5 247 835 A. In thestate of the art, however cutting systems in the form of lasers are usedfor fabric-severing or for loop-cutting by the forming of felt cloth.

In a further embodiment of the invention, the cutting laser shall befitted with an optical system that converts an emitted laser beam into aflat beam.

In order that a low-energy laser shall suffice, its beam normally mustbe focused onto a comparatively small spot. As regards threads, such arequirement may entail problems because of the practical difficulty ofprecisely aligning a filling thread to be cut with the focus of thelaser. This difficulty is circumvented by transforming the laser beaminto a Fat beam. The flat beam may be positioned so that its widthdirection shall run transversely to that of the thread, and accordinglypositioning the thread and/or the laser will not raise problems.

DESCRIPTION OF DRAWINGS

Further features and advantages of the invention will be evident fromthe description below and from the illustrative embodiment shown in thedrawing.

FIG. 1 is a schematic view of an airjet loom fitted with a cuttingsystem of the invention, and

FIG. 2 shows a laser with an optical system converting a laser beam intoa flat beam.

DETAILED DESCRIPTION

A fabric 10 is woven from warp threads 11 and filling threads 12 on aweaving machine shown in very schematic form in FIG. 1. In a manner notshown in detail, the warp threads 11 are periodically raised and loweredby shed-forming elements in order to form sheds into which the fillings12 may be inserted. Following insertion, the filling thread 12 is beatenby a reed 13 against the fabric edge or fell line. The reed 13 ismounted on a batten profile 14 of the batten beam that pivotsto-and-fro. In the embodiment as shown, a main blowing nozzle 15 ismounted on the batten beam profile 14 that accompanies the to-and-fropivoting motion of the reed 13. The main blowing nozzle is shown in muchsimplified form. In practice, preferably two consecutively mounted mainblowing nozzles will be used. Relay nozzles are mounted in a distributedmanner in a transverse direction across the reed 13 and these relaynozzles are supplied with compressed air to help transport the fillingthreads within the shed to the opposite side.

By means of a cutting system 16, the inserted filling thread 12 beatenagainst the fell line is cut from the filling thread segment 12′remaining within the main blowing nozzle 15. Thereupon the reed 13 andthe main blowing nozzle 15 together with the filling 12′ will pivotbackward. As soon as a new shed has been opened, a new filling insertiontakes place, and this time the filling thread 12′ will be inserted. Asalready stated above, the weaving machine is shown in a very simplifiedmanner. In practice several main blowing nozzles 15 are normally used inan adjoining and superposed manner in order to insert several fillingthreads of different types and/or colors. A number of main blowingnozzles may be used even when only identical fillings are inserted, forexample to increase the operational rate.

The end of the filling 12′ currently being kept ready is situated withina moving air stream. The purpose of this air stream is to support theready filling 12′ in such a way that it cannot recoil back out of themain nozzle 15. While this air stream holding the filling 12′ is weakerthan that used to insert it, this weaker air stream nevertheless maytend to unravel the end of the ready filling 12′, especially if thereshould be a weaving pause. This phenomenon is especially troubling whenthe filling threads are filament threads having no or little twist. Suchfilament threads for example, consist of a plurality of thin individualfilaments extending parallel against each other and being fused togetherat distinct, spaced locations. Such a filament thread may unravel in thevicinity of its end and thus there is a danger that when it is insertedinto the shed, it will snag on the reed's teeth. Also, this phenomenonproduces an unattractive appearance of the woven fabric at the side ofthe cloth opposite the insertion side.

To circumvent the above drawbacks, the cutting system 16 is providedwith a pulsed laser cutting system. This laser, which is pulsed, may bea solid-state laser or preferably a gas laser and it cuts the filling ina very short time. During cutting, a comparatively large heat isdissipated and melts synthetic threads or synthetic components, wherebythe ends of the fibers or filaments may be fused together. Even thoughthe blowing air which continues being expelled from the main blow nozzle15 causes rapid cooling, the intense heat generated by the laser willnevertheless induce melting. Accordingly the end of the ready fillingthread 12′ shall remain united.

Moreover, the laser cutting system has the advantage of rapid responsetime and very quick cutting of the filling thread. As a result, thecutting procedure can be timed very accurately in relation to operatingrequirements. This feature also is advantageous when applied to othertypes of weaving machines, for instance, gripper looms. As regardsgripper looms, an inserted filling thread may be severed from a readyfilling thread only after it has been seized and carried along by thegripper for further insertion. It is important in this respect that thetime of cutting be very precisely matched to that time at which thefilling thread is clamped onto and carried along by the gripper for itsinsertion.

The laser cutting beam is tightly focused in order to minimize laserpower consumption as much as possible. Illustratively such minimizationcan be implemented using an optical system including spherical focusinglens elements. On the other hand, point-focusing creates a problem inpositioning the laser because the filling thread has a relatively smalldiameter. Accordingly, an optical system 17 of special lens elements maybe used, for example a cylindrical lense. Such optical system 17converts the laser beam into a flat beam 18. The flat beam 18 isoriented in such a way that its length direction runs transversely tothe longitudinal axis of the filling thread 12, 12′ to be cut.

The laser system 16 offers still another advantage in that the distancebetween the main blowing nozzle 15 and the reed 13 may be keptcomparatively small because the laser cutting beam virtually requires nospace. Still another advantage of the system 16 of the invention is thelack of moving parts that are susceptible to wear, and as a resultlasting and accurate operation is assured.

1. A weaving machine comprising: a main weft thread blowing nozzle; areed for beating up weft threads inserted into a shed of the weavingmachine; a laser arranged to emit a laser cutting beam directed to anarea where a beat up weft thread is located opposite an outlet of theblowing nozzle between the main blowing nozzle and the reed whereby thedistance between the outlet of the main blower nozzle and reed may bekept comparatively small.
 2. A weaving machine as claimed in claim 1,wherein said laser cutting beam is configured as a flat beam.
 3. Theweaving machine as claimed in claim 2, wherein said flat beam isoriented so that it extends transversely of the longitudinal axis of abeat up weft thread.